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The U.S. Preventive Services Task Force (USPSTF) signaled that aspirin may be appropriate to initiate for primary cardiovascular prevention in some high-risk adults ages 40 to 59, but not for those 60 and older.

The draft recommendation statement is a shift from the 2016 guidance, which called for low-dose aspirin for people in their 50s who have a 10% or greater 10-year cardiovascular disease (CVD) risk and individualized decisions for those in their 60s with similar risk.

At the time, evidence for people in their 40s was deemed insufficient to make a recommendation.

Since then, new randomized controlled trials and age distribution data from the Women's Health Study became available, showing that the almost 22,000 participants younger than 50 years didn't have a significantly different CVD outcome response to aspirin than the more than 37,000 participants ages 70 and older.

The task force issued a new "C" recommendation to individualize the decision to initiate low-dose aspirin for primary prevention of CVD in adults ages 40 to 59 with a 10% or greater 10-year CVD risk using the American College of Cardiology/American Heart Association (ACC/AHA) Pooled Cohort Equations.

"Evidence indicates that the net benefit of aspirin use in this group is small," the statement noted. "Persons who are not at increased risk for bleeding and are willing to take low-dose aspirin daily are more likely to benefit."

A key driver for the new "D" recommendation against starting aspirin for people ages 60 and older with no history of heart disease was the ASPREE trial.

In that randomized trial of primary prevention in a population nearly all 70 years and older, daily aspirin not only failed to improve disability-free survival but also increased all-cause mortality, driven by cancer deaths. The CVD composite outcome likewise failed to show an advantage for 100-mg aspirin over placebo (HR 0.95, 95% CI 0.83-1.08).

The USPSTF's microsimulation model showed a modest net benefit in both quality-adjusted life-years and life-years gained with primary prevention aspirin use in both men and women ages 40 to 59 with a 10% or greater 10-year CVD risk. For initiation in those ages 60 to 69, the model showed anywhere from a slight loss to a slight gain in quality-adjusted life-years depending on CVD risk level and a general loss in life-years. Starting aspirin at ages 70 to 79 dropped both quality-adjusted life-years and life-years overall, even in those with up to a 20% 10-year CVD risk.

The group's systematic review also showed a reduction in risk of nonfatal myocardial infarction and nonfatal stroke, increased risk of major gastrointestinal bleeding and intracranial hemorrhage, and no impact on CVD mortality. Not enough evidence turned up to determine if aspirin reduced colorectal cancer incidence, the task force wrote in the draft recommendation statement.

Aspirin dose didn't appear to make a difference, so the USPSTF argued that a "pragmatic approach would be to use 81 mg/d, which is the most commonly prescribed dose in the United States."

The draft recommendations differ from those of the ACC/AHA, which advise that low-dose aspirin use be considered for primary prevention of atherosclerotic CVD at ages 40 to 70 in the setting of elevated CVD risk without increased risk of bleeding. These professional society recommendations agree on no routine aspirin prescribing for primary prevention of CVD in adults over age 70.

In the current therapeutic environment, "the overall benefit of aspirin is small -- in most adults the benefit of protection against heart attacks and strokes is offset by the potential risk of bleeding caused by aspirin," AHA president Donald M. Lloyd-Jones, MD, ScM, said in a statement from the organization. "As a result, aspirin should be used rarely to help prevent heart attacks and stroke among adults ages 40-70 without known cardiovascular disease."

The American Academy of Family Physicians has backed the previous 2016 USPSTF recommendation on aspirin.

The draft recommendations are open for public comment until November 8.

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